An anisotropic electrically conductive film having electrically conductive particles dispersed in an electrically insulating resin binder is widely used for mounting electronic components such as IC chips on a wiring board and the like. However, in such an anisotropic electrically conductive film, it is known that the electrically conductive particles are present in a state of being connected or aggregated with each other. Therefore, in the case where the anisotropic electrically conductive film is applied to the connection between the terminals of the wiring board and the terminals of the IC chip having narrowed pitches upon miniaturizing and reducing the weight of electronic devices, a short circuit may occur between the adjacent terminals due to the electrically conductive particles present in a state of being connected or aggregated in the anisotropic electrically conductive film.
Conventionally, a film, in which electrically conductive particles are regularly arranged, is proposed as an anisotropic electrically conductive film adapted to such a narrow pitch. For example, an anisotropic electrically conductive film obtained as follows has been proposed: An adhesive layer is formed on a stretchable film and the electrically conductive particles are densely filled in a single layer on the surface of the adhesive layer. The film is then biaxially stretched until the distance between the electrically conductive particles becomes a predetermined distance to arrange the electrically conductive particles regularly. Then, an electrically insulating adhesive base layer, which is a constituent element of the anisotropic electrically conductive film, is pressed against the electrically conductive particles, and the electrically conductive particles are transferred to the electrically insulating adhesive base layer (Patent Literature 1). Alternatively, the anisotropic electrically conductive film obtained as follows has also been proposed: Electrically conductive particles are dispersed on a concave portion forming surface of the transfer mold having a concave portion on its surface. The concave portion forming surface is then squeezed to hold the electrically conductive particles in the concave portion, and the adhesive film formed with the adhesive layer for transferring is pressed thereon from above to primarily transfer electrically conductive particles to the adhesive layer. Next, an electrically insulating adhesive base layer, which is a constituent element of the anisotropic electrically conductive film, is pressed against the electrically conductive particles deposited on the adhesive layer, and the electrically conductive particles are transferred to the electrically insulating adhesive base layer (Patent Literature 2). In these anisotropic electrically conductive films, generally, an electrically insulating adhesive cover layer is laminated on the surface of the electrically conductive particle side to cover the electrically conductive particles.